The following information is provided to assist the reader in understanding technologies disclosed below and the environment in which such technologies may typically be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless clearly stated otherwise in this document. References set forth herein may facilitate understanding of the technologies or the background thereof. The disclosure of all references cited herein are incorporated by reference.
The use a coolant or cutting oil (combined as “coolant” in body) in metal cutting increases the efficiency of the cutting tool. Unfortunately the coolant is contaminated with metallic particulate during the cutting process. The coolant is most often pumped in a closed loop through the machine tool, onto the tool/part. The coolant then flows back into the metal cutting machine's sump. To prevent damage to the part, the tool and the metal cutting machine, these particles should be removed before the coolant is pumped back through the metal cutting machine. In the past, it has been difficult, time consuming and/or expensive to remove these particulates from the coolant. The most common filtration system in a metal cutting machine is a very coarse (3000 micron) removable baffle with relatively large holes that catch only the large metal shavings. These perforated baffles require frequent manual cleaning that cause machine downtime. When these perforated baffles are removed for frequent cleaning, dirty coolant and metal waste freely flows from the “dirty side” of the coolant tank to the “clean side”. This system is so inefficient that the “clean side” often fills up with inches of abrasive metal waste that damages the internal components of the metal cutting machine. The thick layer of metal waste is also a medium for anaerobic bacteria that are the main reason for coolant degradation and high replacement costs. This high level of anaerobic bacteria can also cause operator dermatitis that in some cases cause lost work and even disability.
In a number of systems, there are rotating drum conveyers that clean coolant in a conveyer system operatively connected to the machine tool, but they operate at very low pressure (15-20 psi.) and are large, mechanically complex and inefficient. These drum filters are so large that they cannot be used in the majority of metal cutting machines.
High-pressure coolant (for example, at approximately 1000 psi.) has become increasingly popular as a way to improve metal cutting efficiency. The high-pressure coolant is typically plumbed to the metal cutting machine through a hydraulic manifold with at least one outlet to the metal cutting machine and one outlet that is typically referred to as the “dump” that goes to atmosphere in a high-pressure coolant tank or a metal cutting machine tank. Such an arrangement is required so that the coolant flow can be stopped whenever the metal cutting machine changes state. These changes of state include, for example, any tool change, part change or simply turning the metal cutting machine off currently, at each of these changes of state, the valve that is open to the metal cutting machine typically closes very quickly (for example, in approximately 80-100 milliseconds) to prevent damage to the metal cutting machine's internal components. A “dump” valve of the high-pressure coolant system opens just as quickly and at the same time to harmlessly divert all of the residual pressure and coolant volume to the high-pressure coolant system tank or the machine tool sump/tank.
A high-pressure coolant system typically includes a positive displacement pump powered by a 3 phase motor. When the valve that supplies the metal cutting machine with coolant quickly closes in 80 milliseconds, it takes a few seconds for the energy of the rotating mass of the pump parts, the motor and the pressurized coolant to dissipate as waste energy through the dump valve into the sump or tank.